Industrial boilers, such as oil-fired, coal-fired and trash-fired boilers in power plants used for electricity generation and waste incineration, as well as boilers used in paper manufacturing, oil refining, steel and aluminum smelting and other industrial enterprises, are huge structures that generate tons of ash while operating at very high combustion temperatures. These boilers are generally characterized by an enormous open furnace in a lower section of the boiler housed within walls constructed from heat exchanger tubes that carry pressurized water, which is heated by the furnace. An ash collection and disposal section is typically located below the furnace, which collects the ash and carts it away for disposal, typically using a hopper and a conveyor or rail car.
There is a high demand for thermal energy produced by these large industrial boilers, and they exhibit a high cost associated with shutting down and subsequently bringing the boilers back up to operating temperatures. For these reasons, the boilers preferably run continuously for long periods of time, such as months, between shut down periods. This means that large amounts of ash, which is continuously generated by the boiler, must be removed while the boiler remains in operation. Further, fly ash tends to adhere and solidify into slag that accumulates on high-temperature interior boiler structures, including the furnace walls, the superheater platens, and the other heat exchangers of the boiler. If the slag is not effectively removed while the boiler remains in operation, it can accumulate to such an extent that it significantly reduces the heat transfer capability of the boiler, which reduces the thermal output and economic value of the boiler. In addition, large unchecked accumulations of slag can cause huge chunks of slag to break loose, particularly from the platens, which fall through the boiler and can cause catastrophic damage and failure of the boiler. The slag accumulation problem in many conventional boilers has been exacerbated in recent years by increasingly stringent air quality standards, which have mandated a change to coal with a lower sulphur content. This low-sulphur coal has a higher ash content and produces more tenacious slag deposits that accumulate more quickly and are more difficult to remove, particularly from the superheater platens.
To combat this problem, the industry has developed increasingly sophisticated boiler cleaning equipment. In particular, steam and multi-media (e.g., water and steam) sootblowers have been developed for periodically cleaning the heat exchangers while the boiler remains in operation. These sootblowers generally include lance tubes that are inserted into the boiler adjacent to the heat exchangers and operate like large pressure washers to clean the heat exchangers with a cleaning fluid, such as water, steam, or both water and steam, while the boiler remains in operation. These sootblowers are generally characterized by rotating and linearly traveling lance tubes that blast the cleaning fluid in a corkscrew pattern to clean as wide an area as possible as the lance advances. To allow the lance tube to move freely while transporting the steam, the lance tube is typically received telescopically over an open steam tube. This allows the steam tube to deliver steam into an interior cavity of the lance tube as the lance rotates and moves telescopically on the steam tube.
The configuration described above creates moving steam joint between the steam tube and the lance that must remain sealed as the lance rotates and moves telescopically along the steam tube. This steam joint is typically sealed by a set of sacrificial gaskets known as a “packing,” which consisting of a series of rings constructed from a deformable, heat-resistant material, such as an oil impregnated graphite material known in the trade as GRAPHOIL™. TEFLON™ based materials have also been successfully used for sootblower packing.
The packing rings have an inner diameter approximately the size of the steam tube and an outer diameter approximately the size of the inner dimension of a spindle surrounding the packing. The spindle, in turn, supports the lance as the lance rotates and moves linearly along the steam tube. To form a seal, the packing is loaded by a compression plate that is typically biased by spring washers (also called “Belleville washers”). Compression presses the packing material against the spindle and steam tube and thereby causes the packing to deform sufficiently to form a steam-tight seal. The spring washers expand over time to maintain the load on the packing as friction wears away sacrificial packing material. Eventually, the packing becomes spent and must be replaced.
The packing is replaced by sliding the steam tube out the spindle and then picking, prying and scraping the spent packing material out of the spindle. This packing, which has been mashed an repeatedly heated and cooled over time, can be difficult to coax out of the spindle. For this reason, technicians have been known to resort to non-recommended packing removal methods, such as opening the steam valve adjacent to the packing in an attempt to blow the packing out of the spindle. It should be appreciated that the sootblowers are typically used continually every day (e.g., hourly) while the boiler is in operation. For this reason, an extended packing replacement process, as occurs when technicians grapple with picking and scraping jammed packing out of the spindle, can interfere with the boiler cleaning regimen.
Accordingly, a continuing need exists for improved packing and packing replacement procedures for sootblowers used to periodically clean industrial boilers. More specifically, a need exists for a sootblower packing that lasts longer and can be removed and replaced faster, easier and more safely than a conventional sootblower packing.